96 -M. NOBILI ON COLOURS, AND ON ‘A NEW CHROMATIC SCALE 
the attempts hitherto made give little or no hope that the best executed 
copies can give more than an imperfect idea of the original colours. 
The effect produced by these tints when disposed in the order set 
forth in the scale baffles description; it bears a resemblance however 
to that produced on the ear by a scale of semitones executed by a per- 
fect voice. I have shown my scale to several, and especially to those eru- 
dite and learned persons who have favoured me with a passing visit at 
Reggio. In all it excited but one feeling of delight. So gradual indeed 
is the transition from one tint to another and such the harmony with 
which they are blended, that if the eye be accidentally turned away, it 
reverts inamoment as if moved by an irresistible desire to gaze still longer 
on the display. Thisstatement is no exaggeration. It is but the mere fact, 
in respect to which a language much more glowing would be perfectly 
consistent with truth: so overpowering is the charm which, if I may use 
the expression, pervades the scale of our coloured plates. 
Chromatic Scale. 
This scale consists of forty-four tints, each of which is applied to a plate 
of steel. A Table subjoined to this Memoir exhibits the forty-four plates 
arranged one under the other in a column, and opposite to each number 
is the name of its peculiar tint. These tints are disposed in the same 
order as the layers or thin plates by which they are produced. The co- 
lour of the thinnest plate is placed first, and the others follow in the order 
of the progressively increasing thickness of the plates*. In this arrange- 
ment I cannot be mistaken, because the layers or thin plates which 
produce the several colours are all applied by the same electro-chemical 
process. The pile, the solution, the distances remain exactly the same. 
There is nothing variable but the duration of the action, which in respect 
to the layer No. 1. is very short, a little longer in respect to the second, 
and increases progressively from the lowest to the highest number. 
Other criterions also contribute to verify the accuracy with which its 
place is assigned to each tint. 
These colours are produced by very thin layers or plates analogous to 
those which produce the colours in soap-bubbles and the rings observed 
* The numerals placed within parentheses (in the Table) are designed to 
indicate the thickness of the plates which produce the different colours. These 
numbers are taken from Newton’s table, the fractional parts only being omitted. 
The numbers are those which apply to thin layers of water. The unit of mea- 
sure is the millionth part of an English inch. Our scale should then commence 
with a layer measuring four of these units in thickness and end with a layer 
measuring thirty, if we suppose our electro-chemical layers to possess the same 
refractive power as water. It is probably somewhat less. At all events it is 
useful to have these numbers immediately before our eyes, in order that we may 
know, if not the absolute, at least the relative thickness of the attenuated layers 
which effectively cover our plates of steel. 
lie MF ~ 
